Today, with swichmode supplies, I think DC would make most sense. We lose much power to frequency deviation and inductive loads causing phase shift.
It would also make sense to have a high voltage and low voltage nets in houses. Low voltage for lighting and other low power equipment. High voltage for power hungry equipment. For example 48V and 480V.
Very old US light switches often had both AC and DC current ratings, and the DC rating was noticeably lower due to the arcing problem, even with fast-acting snap action.
My grandfather worked in a Chicago office building that had 110V DC service even into the 1960s. He had to be careful to buy fans, radios, etc. that could run on DC.
Do we really lose much to phase shift? Increasing apparent load only causes a tiny fraction of that much waste, and local compensation isn't very expensive.
DC or a significant frequency boost would be good inside a house for lights and electronic items. Not so great for distribution.
I'm not convinced multiple voltages would be a net benefit outside of the dedicated runs we already do for big appliances.
It would also make sense to have a high voltage and low voltage nets in houses. Low voltage for lighting and other low power equipment. High voltage for power hungry equipment. For example 48V and 480V.